M2 PSU ignition/ACC power up problem

Hello,
I have an M2 PSU powering an miniITX-SN mother board and am having trouble getting the power on ignition working properly. If I turn the key to the ACC line (hooked up to the blue ACC or IGN wire from a wiring harness for my 02 Jeep Gnd Cherokee) the computer boots up great. Or, if I go strait to crank the engine, the computer boots up great. The problem is if I have the computer running on ACC and then start the car the computer reboots. This also happens when I have the car running and I turn it off. Even stranger, if I have the engine off running the computer on ACC and then turn ACC off, then the computer reboots.
I have:
Tried multiple jumper changes on the M2 to no avail.
Rechecked my power wiring (10 guage + and - wire directly to battery and an additional ground wire to chassis ground)
With the engine and computer running if I disconnect the IGN wire on the M2, everything works as advertized. ('puter stays running till the M2 jumper selected power down is initiated)
Got a new battery with 850 CCA available

Sounds to me like a power problem. I thought the M2 should be able to hack it. Any ideas?

I had one power supply that would lock up my notebook whenever I powered off my running engine. To me that suggests there was some electrical noise (spike) that my power supply passed on through to my notebook.

Switching over to the M2-ATX-160watt power supply and replacing the notebook with a miniITX MB solved the problem for me.

Definitely have the power button connected to the correct pins (not sure the polarity, but it's to the pwr pin). The thing that makes me think that is not it is that if I disconnect the IGN wire manually everything works like a champ. That's what makes me think it's a pwr problem. Isn't the M2 supposed to be good at that. Any idea on how to try to soften the blow if you will of the power cycle. And would such a thing happen if I just turn from ACC running computer directly to off... that shouldn't give too big a spike, or would it?